SPECIATION OF METALS IN YAMUNA RIVER SEDIMENTS

The chemical forms of cadmium, copper, lead and zinc have been determined using the fractionation scheme of Tessier et al. in the bed sediments of River Yamuna. Sediment characteristics do not show any significant variations except that carbonate content is consistently higher in the post-monsoon season. Silicon and aluminium are the most abundant elements followed by K, Na, Ca, Fe, Mg and Mn in that order, the essential minerals being quartz and biotite. The speciation profiles for a particular metal show a similar trend throughout the stretch with no significant spatial variations. Cadmium is mostly associated with carbonate content and thus has a possibility of becoming readily bioavailable. Major fraction of copper is bound to organic matter while that of zinc to Fe-Mn oxide. Thus they cannot be easily leached out and may pose less environmental risk. Major percentage of lead is found in the Fe-Mn oxide fraction; moderate contributions being made by carbonate and residual fractions. The total lead in the sediments is higher, therefore even a small fraction of lead bound to carbonate content can pose problems to the ecosystem. There are good correlations between the different constituents and the major metal fractions associated with it.